Apparent geographic and atmospheric influences on raindrop sizes and rainfall kinetic energy

ABSTRACT:

Rainfall kinetic energy was calculated from average drop size distributions measured at six locations. Median raindrop diameters in North Carolina, New Jersey, and the Marshall Islands tended to be less than those observed in Panama, Indonesia, Washington, D.C., and Zimbabwe. Calculated rainfall kinetic energies for Panama and Indonesia were within 10% of that predicted by the universal soil loss equation (USLE) rainfall energy equation. Calculated rainfall energies for New Jersey, the Marshall Islands, and North Carolina ranged from 5% to 28% less than that predicted by the USLE rainfall energy equation. An uncertainty interval of 15% to 30% of the estimated rainfall energy value is suggested to reject uncertainties in geographic differences in raindrop sizes. Increasing the rainfall energy estimate by 7% for each 1,000 m (3,280 feet) of elevation above sea level is suggested to account for increased raindrop velocity under reduced atmospheric pressure. Additional research is recommended on the geographic effects on raindrop sizes and raindrop detachment of soil, particularly in West Africa, at higher elevations and for periods exceeding 2 years.